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const debug = @import("debug.zig");
const assert = debug.assert;
const math = @import("math.zig");
const mem = @import("mem.zig");
const Allocator = mem.Allocator;
const want_modification_safety = !@compileVar("is_release");
const debug_u32 = if (want_modification_safety) u32 else void;
pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn(key: K)->u32,
comptime eql: fn(a: K, b: K)->bool) -> type
{
struct {
entries: []Entry,
size: usize,
max_distance_from_start_index: usize,
allocator: &Allocator,
// this is used to detect bugs where a hashtable is edited while an iterator is running.
modification_count: debug_u32,
const Self = this;
pub const Entry = struct {
used: bool,
distance_from_start_index: usize,
key: K,
value: V,
};
pub const Iterator = struct {
hm: &Self,
// how many items have we returned
count: usize,
// iterator through the entry array
index: usize,
// used to detect concurrent modification
initial_modification_count: debug_u32,
pub fn next(it: &Iterator) -> ?&Entry {
if (want_modification_safety) {
assert(it.initial_modification_count == it.hm.modification_count); // concurrent modification
}
if (it.count >= it.hm.size) return null;
while (it.index < it.hm.entries.len; it.index += 1) {
const entry = &it.hm.entries[it.index];
if (entry.used) {
it.index += 1;
it.count += 1;
return entry;
}
}
@unreachable() // no next item
}
};
pub fn init(hm: &Self, allocator: &Allocator) {
hm.entries = []Entry{};
hm.allocator = allocator;
hm.size = 0;
hm.max_distance_from_start_index = 0;
// it doesn't actually matter what we set this to since we use wrapping integer arithmetic
hm.modification_count = undefined;
}
pub fn deinit(hm: &Self) {
hm.allocator.free(hm.entries);
}
pub fn clear(hm: &Self) {
for (hm.entries) |*entry| {
entry.used = false;
}
hm.size = 0;
hm.max_distance_from_start_index = 0;
hm.incrementModificationCount();
}
pub fn put(hm: &Self, key: K, value: V) -> %void {
if (hm.entries.len == 0) {
%return hm.initCapacity(16);
}
hm.incrementModificationCount();
// if we get too full (60%), double the capacity
if (hm.size * 5 >= hm.entries.len * 3) {
const old_entries = hm.entries;
%return hm.initCapacity(hm.entries.len * 2);
// dump all of the old elements into the new table
for (old_entries) |*old_entry| {
if (old_entry.used) {
hm.internalPut(old_entry.key, old_entry.value);
}
}
hm.allocator.free(old_entries);
}
hm.internalPut(key, value);
}
pub fn get(hm: &Self, key: K) -> ?&Entry {
return hm.internalGet(key);
}
pub fn remove(hm: &Self, key: K) {
hm.incrementModificationCount();
const start_index = hm.keyToIndex(key);
{var roll_over: usize = 0; while (roll_over <= hm.max_distance_from_start_index; roll_over += 1) {
const index = (start_index + roll_over) % hm.entries.len;
var entry = &hm.entries[index];
assert(entry.used); // key not found
if (!eql(entry.key, key)) continue;
while (roll_over < hm.entries.len; roll_over += 1) {
const next_index = (start_index + roll_over + 1) % hm.entries.len;
const next_entry = &hm.entries[next_index];
if (!next_entry.used || next_entry.distance_from_start_index == 0) {
entry.used = false;
hm.size -= 1;
return;
}
*entry = *next_entry;
entry.distance_from_start_index -= 1;
entry = next_entry;
}
@unreachable() // shifting everything in the table
}}
@unreachable() // key not found
}
pub fn entryIterator(hm: &Self) -> Iterator {
return Iterator {
.hm = hm,
.count = 0,
.index = 0,
.initial_modification_count = hm.modification_count,
};
}
fn initCapacity(hm: &Self, capacity: usize) -> %void {
hm.entries = %return hm.allocator.alloc(Entry, capacity);
hm.size = 0;
hm.max_distance_from_start_index = 0;
for (hm.entries) |*entry| {
entry.used = false;
}
}
fn incrementModificationCount(hm: &Self) {
if (want_modification_safety) {
hm.modification_count +%= 1;
}
}
fn internalPut(hm: &Self, orig_key: K, orig_value: V) {
var key = orig_key;
var value = orig_value;
const start_index = hm.keyToIndex(key);
var roll_over: usize = 0;
var distance_from_start_index: usize = 0;
while (roll_over < hm.entries.len; {roll_over += 1; distance_from_start_index += 1}) {
const index = (start_index + roll_over) % hm.entries.len;
const entry = &hm.entries[index];
if (entry.used && !eql(entry.key, key)) {
if (entry.distance_from_start_index < distance_from_start_index) {
// robin hood to the rescue
const tmp = *entry;
hm.max_distance_from_start_index = math.max(hm.max_distance_from_start_index,
distance_from_start_index);
*entry = Entry {
.used = true,
.distance_from_start_index = distance_from_start_index,
.key = key,
.value = value,
};
key = tmp.key;
value = tmp.value;
distance_from_start_index = tmp.distance_from_start_index;
}
continue;
}
if (!entry.used) {
// adding an entry. otherwise overwriting old value with
// same key
hm.size += 1;
}
hm.max_distance_from_start_index = math.max(distance_from_start_index, hm.max_distance_from_start_index);
*entry = Entry {
.used = true,
.distance_from_start_index = distance_from_start_index,
.key = key,
.value = value,
};
return;
}
@unreachable() // put into a full map
}
fn internalGet(hm: &Self, key: K) -> ?&Entry {
const start_index = hm.keyToIndex(key);
{var roll_over: usize = 0; while (roll_over <= hm.max_distance_from_start_index; roll_over += 1) {
const index = (start_index + roll_over) % hm.entries.len;
const entry = &hm.entries[index];
if (!entry.used) return null;
if (eql(entry.key, key)) return entry;
}}
return null;
}
fn keyToIndex(hm: &Self, key: K) -> usize {
return usize(hash(key)) % hm.entries.len;
}
}
}
fn basicHashMapTest() {
@setFnTest(this);
var map: HashMap(i32, i32, hash_i32, eql_i32) = undefined;
map.init(&debug.global_allocator);
defer map.deinit();
%%map.put(1, 11);
%%map.put(2, 22);
%%map.put(3, 33);
%%map.put(4, 44);
%%map.put(5, 55);
assert((??map.get(2)).value == 22);
map.remove(2);
assert(if (const entry ?= map.get(2)) false else true);
}
fn hash_i32(x: i32) -> u32 {
*(&u32)(&x)
}
fn eql_i32(a: i32, b: i32) -> bool {
a == b
}
|
